Sambo agreement (Pre-nup) questions

Apartment, savings, and other assets.

I am planning to move in with my girlfriend after the summer, and therefore, I have started to think about the legal consequences of this change in our life. We are moving together to my rented apartment (Only me in the contract and I will pay the totally of the rent by myself). I wonder if in case of breakup (I know that nobody expects to break up when moving in together. However, look at the divorce rates...) I will be able to keep the rented apartment for me. In addition, I have inhered properties and money. I am afraid if I have to state these assets in a prenup / sambo agreement to protect them in case of future break-up. Could you throw some light into this issue?